The stability of the ionic liquid [MeBu3N][Tf2N], dry or after contact with water (where [MeBu3N]+ is the methyltributylammonium cation and [Tf2N](-) is the bistriflimide anion), was studied under 137Cs gamma irradiation in argon and in air. In a quantitative study with an absorbed dose of 2 MGy this ionic liquid was highly stable regardless of the radiolysis conditions. The radiolytic disappearance